Now to get the full story, do you have to read every single one of those extra comic books, or can you just read the main mini series?

One thing I've never liked about comics is that you have to read books outside of the specific series you might be interested in and it becomes a complete mess. How would you even figure it out if you didn't have the internet?

Main series for the full story. Tie-ins just tell it from a different perspective. You'll be fine if you read the main series and nothing else.